The present invention relates to the structure of a rotor in a rotary electric machine suitable for use in a turbine generator or the like.
Generally, field windings for DC exciting a generator are wound round a cylindrical rotor of a rotary electric machine such as a turbine generator. Plural slots are axially formed in the other portion than magnetic pole portions of an iron core of the rotor. The slots are formed at equal intervals in the circumferential direction of the rotor.
The field windings are inserted into the slots and are held by wedges. The wedges each have a slant face formed at a predetermined angle relative to the radial direction of the rotor core and are fitted in the slots. Teeth, which are comb teeth-like, are formed between adjacent slots and have slant faces for abutment against the slant faces of the wedges to retain each wedge in a fitted state between adjacent teeth.
The rotor in a rotary electric machine constructed as above is described, for example, in Japanese Patent Laid Open No. 11-299143.
Centrifugal forces of windings and wedges fitted inside the slots are applied to the teeth and a large force is applied constantly to the teeth-wedge fitted portions. This force becomes large particularly when the application of load and the removal thereof are repeated at the time of turning ON and OFF of the rotor.
On the other hand, the rotor has two or four unslotted portions called magnetic pole portions (magnetic poles). Usually, in many cases, an iron wedge is inserted into a slot located near a magnetic pole to stabilize the distribution of a magnetic field. Wedges made of aluminum, which is lighter than iron, are inserted into slots positioned apart from the magnetic pole portions. Therefore, a problem is encountered such that a larger centrifugal force is applied to teeth located near the magnetic pole portions relative to the other teeth.
Recently, for reducing the size of a rotor by enlarging a magnetic field generated in a field system, slots are set large in depth and width to receive a larger number of windings therein. Consequently, the application of a larger centrifugal force to teeth located near magnetic pole portions is becoming more and more conspicuous.
The present invention has been accomplished in view of the above-mentioned problems and it is an object of the invention to provide a rotor in a rotary electric machine capable of diminishing stress concentration on teeth located near magnetic poles, thereby preventing damage of the teeth, and capable of deepening slots, thereby enlarging a magnetic field generated in field windings.
The present invention is characteristic in that a rising position of each slant face of teeth forms a circular arc and, in a preset number of teeth located near magnetic pole portions of the rotor, the radius of curvature (radius) of the circular arc formed at the rising position of each slant face is set larger than that of the circular arc formed at the rising position of each slant face in the remaining teeth, the teeth having the slant faces for abutment against slant faces of wedges to retain the wedges in a fitted state between adjacent teeth, the slant faces of the wedges being formed at a predetermined angle relative to the radial direction of the rotor.
In other words, according to the present invention, a preset number of teeth located near each of magnetic pole portions are constituted so as to be decreased in stress at rising positions of their slant faces.
In the present invention, in a preset number of teeth located near magnetic pole portions, the radius of a circular arc formed at each slant face rising position is set larger than that of a circular arc formed at each slant face rising position in the remaining teeth, whereby the stress in each slant face rising position of the teeth can be decreased and hence it is possible to prevent damage of the teeth. As a result, it is possible to deepen slots and enlarge a magnetic field generated in field windings, thus permitting the reduction in size of the rotor.